The invention relates to OFDM communication systems, and in particular, to a channel estimation method for DVB-T system.
FIG. 1a shows conventional DVB-T symbols. The horizontal rows are DVB-T symbols comprising a plurality of sub-carriers, arranged in vertical time direction. The white nodes frequency direction interpolator 110 carry data, and the black nodes such as 210a, 210b and 210c, are pilots. The distribution of pilots varies in time direction, periodically repeating every four symbols. Conventionally, pilots are utilized to estimate the channel. For example, a pilot response at the fifth row (t=5) is generated by interpolation of adjacent pilots in time direction. The pilots 210a and 230a interpolate the pilot 220a, the pilots 210b and 230b interpolate the pilot 220b, and the pilots 210c and 230c interpolate the pilot 220c. The interpolation may be a linear interpolation, and is also referred to as a time direction interpolation (TDI).
FIG. 1b shows a pilot response obtained from the DVB-T symbols of FIG. 1a. The pilots H0 to H5 are shown at an interval. The channels for the sub-carriers therebetween, such as Ha and Hb, are estimated by frequency direction interpolation. Conventionally, the frequency direction interpolation may be accomplished through various algorithms, such as linear interpolation, second order interpolation, third order interpolation, bi-linear interpolation and fixed finite impulse response (FIR) interpolation. The estimated channel is utilized to restore transmitted data in the sub-carriers in an equalization process, therefore an efficient channel estimation method can improve the DVB-T receiver performance.